Valid Monday October 24, 2016 to Friday November 04, 2016
US Hazards Outlook
NWS Climate Prediction Center College Park MD
EDT October 21 2016Synopsis
: A strong low-pressure system is
forecast over southeastern Canada during the early portions of the outlook
period. High pressure is forecast to build in over the Midwest, then slide
eastward as an active pattern emerges over the Great Plains. A strong
low-pressure system is forecast to impact the Pacific Northwest, with more
troughing over the eastern Pacific setting the stage for an active period for
California and the Great Basin. A potent surface low-pressure system is
forecast over the Bering Sea during the middle of next week while another
strong area of surface low pressure is anticipated over the Gulf of Alaska Oct
27. The predicted pattern for Week-2 favors an active pattern from the the West
Coast to the High Plains, with less activity over the southeast U.S.
Summary For Monday October 24 - Friday October
- Heavy rain across portions of California and the
Pacific Northwest, Tue, Oct 25.
- Heavy rain across portions of the Central Great Basin, and California, Fri,
- Heavy rain across portions of the Middle Mississippi Valley, the Great
Lakes, and the Upper Mississippi Valley, Tue-Wed, Oct 25-Oct 26.
- Flooding occurring or imminent across portions of the Southeast and the
- High winds across portions of the Great Lakes, the Mid-Atlantic, the
Northeast, the Central Appalachians, and the Ohio Valley, Mon, Oct 24.
- Heavy precipitation across portions of the Alaska Panhandle and mainland
Alaska, Wed-Thu, Oct 26-Oct 27.
- High winds across portions of mainland Alaska and the Aleutians, Tue-Wed,
Oct 25-Oct 26.
- High winds across portions of mainland Alaska, Thu, Oct 27.
- High significant wave heights for coastal portions of mainland Alaska and
the Aleutians, Tue, Oct 25.
- Severe Drought in the Central Plains, the Mid-Atlantic, the Lower
Mississippi Valley, the Central Great Basin, the Northern Plains, the Tennessee
Valley, the Great Lakes, Hawaii, the Northern Great Basin, the Northeast,
California, the Southern Appalachians, the Southeast, the Central Appalachians,
the Southern Plains, and the Southwest.
A strong low-pressure system is forecast over the Maritime provinces
of Canada this weekend. High winds (exceeding 30 knots) are forecast over the
eastern Great Lakes and Northeast through Monday. Heavy precipitation
associated with this system is likely to be winding down by early next week.
High pressure and warm temperatures are likely to build in over the Great
Plains. Daily high temperatures are likely to be 16-20 degrees F above normal,
but high temperatures are not expected to be threatening to life or property,
so no hazard is depicted.
Troughing forecast to approach the Pacific Northwest from the Gulf of
Alaska is expected to cause the development of areas of surface low pressure
near the region Oct 24-25. Rainfall totals are likely to approach or exceed
hazardous levels across portions of western Washington, Oregon, and Northern
California. Rainfall amounts during this 48 hour period could locally exceed 3
The shortwave is forecast to move from the Central Rockies to the Great
Lakes, contributing to potentially heavy rains from Iowa to the Great Lakes.
Rainfall totals are expected to exceed 1 inch in 24 hours for Oct 25, with
lower probabilities of exceeding that same threshold on the 26th.
A second impulse is forecast to bring an extended period of wet weather to
northern California on Oct 28, with rainfall totals exceeding 2 inches in 24
hours (locally higher amounts in areas where orographic effects are maximized).
The continued influx of shortwaves from the Pacific also increases the odds for
moderate to locally heavy snows over the higher terrain of the Northern
Rockies, for the middle of next week, but uncertainty on the location of the
heaviest snow precludes a depiction of a hazard.
Over the Bering Sea, a very deep trough is expected Oct 25-26. At the same
time, areas of surface low pressure are anticipated over the Bering Sea and
northern Gulf of Alaska. This is expected to lead to significant waves (wave
heights in excess of 20 feet) Oct 25 for parts of the Aleutians and the western
coast of Alaska, and high winds (winds in excess of 40 knots) Oct 25-26 for
parts of western mainland Alaska and the Aleutians. Coastal flooding due to
ocean encroachment along the western coast of Alaska is also possible.
Localized areas of heavy precipitation are likely over western Alaska, although
model guidance has backed off since yesterday with predicted precipitation
totals. The risk to life and property with this predicted system is high.
As that system matures, redevelopment near the triple point, over the Gulf
of Alaska, is likely during Oct 27. Heavy precipitation (snow in the higher
terrain) is likely over southern Alaska and portions of the Alaska Panhandle,
along with high winds (approaching 40 knots, with higher speeds at elevation).
Model output indicate the potential for high winds and coastal erosion for
western Alaska through Oct 29.
The tropical Pacific remains semi-active so the area will need to be
monitored for possible tropical cyclone development. For Saturday October 29 - Friday
The GEFS reforecast-based calibration outputs indicated
continued wet conditions for California and the Great Basin for days 8-10.
Precipitation amounts are likely to be above average, but only locally over the
Northern Sierras does the GEFS reforecast-based calibration indicate a slight
enhancement for the odds of exceeding hazardous thresholds. Additionally, the
models also indicate above average rains for the Central Great Plains and
Midwest, but the odds of exceeding 2 inches in the 8-10 period are not
significantly different than climatology.
Severe, or greater intensity, drought increased slightly in coverage across
the CONUS during the past week. Severe drought is now covering 9.66% of the
CONUS, up from 8.68% the prior week.
Click here to see a display of the GFS Ensemble Forecasts
Please consult local NWS Forecast Offices for short range forecasts and region-specific information.